1. Field of the Invention
The present invention relates to a video printer, and more particularly to a video printer for recording an image on an image-receiving medium and thereafter achieving postprocessing on a surface of the medium, and also to a postprocessing method implemented by the video printer.
2. Description of the Prior Art
For example, in a thermal printer, a dye developing thermally diffusing and transferring characteristics is heated by means of a thermal print head so as to be transferred onto a transfer medium such as paper, thereby recording visible information thereon. The dye is applied on a ribbon or a sheet with a binder. With the dyed surface of the ribbon or sheet brought into contact with the transfer medium, or image-receiving medium, the opposite surface thereof is heated by the thermal print head. The head includes an array of heater elements in which many heating elements are arranged in a line. The heater elements heat portions of the dye on the ribbon or sheet in association with information items to be recorded on the medium. As a result, portions of the dye in the heated locations of the ribbon or sheet are diffused so as to be transferred onto the transfer medium. This type of thermal printer is efficiently applied to a video printer, for example.
In the thermal printer, when the dye is passed from the ribbon or sheet onto the transfer medium, the dye does not completely penetrate into materials constituting the medium. More specifically, the dye accumulates thereon to form a layer on the transfer surface. This consequently lowers the stability of the information recorded on the medium. Moreover, the dye accumulated on the surface develops a metallic luster, which reduces quality of the visibility of the printed image. In addition, since the accumulated portion of the dye is not satisfactorily fixed onto the medium, the dye may often be transferred further therefrom to the surface of another article that is brought into contact with the surface.
Heretofore, as for postprocessing to be accomplished after the dye transfer to increase the durability of the dye layer on an image-receiving medium, an apparatus has been proposed in a co-pending Japanese patent application No. 223560/1988 filed by the same applicant as that of the present application. With the apparatus disclosed in the prior Japanese application, the image-receiving medium is transferred through a gap between a couple of heater rollers rotating with respective opposing surfaces thereof being brought into contact with each other so as to produce a smooth surface on the medium. In the prior art, when paper is used as the recording medium, a satisfactory smooth surface can be expectedly produced on the surface. However, due to a considerably strong heating energy produced, when synthetic paper is adopted as the medium, wrinkles may be formed on a surface opposite to the smoothed front surface. This apparatus has not been suitably incorporated into a hardcopying apparatus such as a video printer for the following reason. The adoption of such prior art apparatus leads to a disadvantage that the size and power consumption of the overall system are increased.
Another co-pending Japanese patent application filed by the same applicant as that of the present application, Nos. 228481/1988 and 228482/1988 have disclosed video printers in which an image-receiving medium already carrying an image recorded is processed to develop luster. In the former application, a dye sheet is used which has a blank area disposed to attain luster on a surface of the image-receiving medium. In the latter, in place of the dye sheet, a lusterring sheet is used to develop luster on the medium surface. In both of the conventional video printers, the postprocessing is limitatively used to obtain the luster. More specifically, the postprocessing cannot be adopted to produce other surfaces such as mat and silky surfaces. In addition, a dye sheet or a postprocessing sheet having a constitution dedicated to the postprocessing has been necessary. Particularly, in a process to eject the image-receiving medium after postprocessing, when the blank area of the dye sheet or the postprocessing sheet tightly fixed on the surface of the medium is peeled off therefrom, it is likely that the surface of the image-receiving medium may be disadvantageously rubbed, thereby forming flaws or defects thereon. In consequence, a high quality cannot be attained for the image recording.